In the case of a portable power tool such as a cut-off saw, belt transmission arrangements have been widely employed as power transmission device for transmitting the power of a driving motor such as an internal combustion engine, hydraulic engine or electric motor, to a rotatable working member such as a rotating cutter. A belt disposed between and wound around a pair of transmission wheels, where a first transmission wheel is connected to the driving motor and a second transmission wheel is connected to the rotatable working member.
Such a belt is relatively stiff, and has to be kept under a predetermined tension in order to minimize transmission and power losses. It is also desired to be able to relatively easily change the belt when it has been worn out or has been broken.
It is previously known to have the transmission wheels mounted to an arm that comprises two components longitudinally movable relative each other, i.e. in the longitudinal direction of the belt, in a co-axial manner. Previously, screw tension devices have been proposed for displacing the two components, see for example US 2009007435. Such screw tension devices may be troublesome and time-consuming to handle, there may be a number of bolts that have to be loosened as well.
It is therefore desirable to provide a secure transmission belt adjustment device that is easily used and ensures a proper belt tension.